The invention relates to a method for coating substrates with materials to be vaporized in a vacuum coating system, wherein the material to be vaporized is heated in a vaporization device, vaporized and deposited on a substrate. The vaporization material is deposited on the substrate by double vaporization using an intermediate carrier, and the intermediate carrier is moved continuously.
The invention furthermore relates to a device for coating substrates with materials to be vaporized, comprising a vaporization device for vaporizing the materials to be vaporized inside a vacuum coating system. The vaporization device is in this case arranged for vaporizing vaporization materials in a first position. Opposite the side of the intermediate carrier intended to receive vapor deposition, a heating apparatus is arranged in a second position in spatial proximity to the substrate. An intermediate carrier is arranged movably between the first and second positions, means being provided for continuous movement of the intermediate carrier.
The coating of substrates with materials to be vaporized, in particular organic materials, in vacuum coating systems is conventionally carried out by means of point sources in which the organic materials are vaporized at a large distance of for example 50 cm from the substrate. In this way, a homogeneous layer thickness of the material deposited on the substrate is achieved.
For instance, DE 10 2005 013 875 A1 discloses a vacuum coating system comprising a heating apparatus, which is suitable for vaporizing organic materials.
Disadvantages with this, however, are primarily the low yield of the vaporization material, which often ranges only in the region of a few percent. This is unacceptable particularly for the case of organic materials, which constitute the main cost factor in the production of OLEDs and organic solar cells.
Methods and devices for co-vaporization of organic materials for the production of OLEDs are furthermore known.
In production systems, line sources are also used which are normally composed of nozzles arranged in a row in a vapor tube. For homogeneous layer deposition, a minimum distance in the centimeter range between the substrate and the vaporizer source is also required in this case, so that the yields usually lie in the range of between 50% and 70%.
DE 101 28 091 C1 discloses a device for coating a flat substrate by using such a line source.
For the production of layers of organic materials on a substrate, devices are known in which layers from different vaporization sources are deposited successively on the substrate.
The various materials are vaporized in different vaporization devices, and introduced into the process chamber through a gas inlet. The composition of the gas phase in the process chamber can be regulated by supplying inert gas or by pumping out. Disadvantages with this device and the associated method are, again, the low yields due to the separation between the vaporizer source and the substrate, particularly when a plurality of materials are vaporized simultaneously.
U.S. Pat. No. 4,748,313 A discloses a method for vaporizing inorganic materials, wherein two rotating drums are used. In a first step, the inorganic material is vaporized and deposited on the surface of the first rotating drum. In relative proximity to this rotating drum, a second rotating drum is arranged on which the substrate to be coated, for instance a film, is arranged. In the region of the shortest distance between the two drums, an electron beam gun is arranged inside the first drum, so that the deposited material is vaporized and deposited on the substrate on the second drum. The disadvantage with this arrangement consists primarily in the use of the electron beam gun, which is unsuitable for use when vaporizing organic materials. Furthermore, it is not possible to coat flat substrates with the device disclosed in U.S. Pat. No. 4,748,313 A.
EP 1 391 532 A1 discloses a method for producing a compact organic pellet for OLED production, the pellet being provided in a roll form. The pellet is subsequently transferred into a vaporization device, where it is heated and vaporized by the heating apparatuses arranged in the heating apparatus while rotating about its own axis. The material thus vaporized is then deposited on the substrate to be coated. A disadvantage in this case is, in particular, the elaborate production of the pellet from the organic materials.
US 2005/0281050 A1 discloses a method and a device for producing OLEDs. The substrates to be coated are conveyed along a transport path through a plurality of coating chambers. At the same time, the vaporization source is moved on a separate transport path between the individual coating chambers, so that a plurality of substrates can be coated in a shorter time. The disadvantage with this device resides primarily in the fact that the device proposed in US 2005/0281050 A1 and the associated method are unsuitable for ensuring continuous coating with the required throughput rates.
WO 2010/045974 A1 discloses a method and a device for coating substrates, wherein the organic material is vaporized and deposited on a carrier. The carrier is subsequently introduced into the vacuum coating chamber, where the organic material is vaporized for a second time and deposited on the substrate to be coated. The carrier is in this case configured in a strip shape from a flexible material. The disadvantage with using strip-shaped intermediate carriers resides primarily in the materials that can be used for the required flexibility, which leads to a great restriction in terms of the organic materials to be deposited.
German Patent Application No. 10 2009 007 587.9 provides a method and a device, the material to be vaporized being deposited on the substrate by double vaporization using an intermediate carrier. In this way, the material to be vaporized is not formed directly on the substrate by vaporization, but instead an intermediate carrier is used.
The material to be vaporized is vaporized for a first time by the vaporization device in a first position and deposited on the intermediate carrier, which is arranged position-variably in spatial proximity to the vaporization apparatus. This coated intermediate carrier is subsequently brought into a second position which lies in spatial proximity to a substrate to be coated, and the vaporization material deposited on the intermediate carrier is vaporized for a second time in the second position and deposited on the substrate. The intermediate carrier is in this case used for receiving the vaporized material and for deposition on the substrate to be coated. By using the intermediate carrier, it is possible to achieve greater yields in the range of 90% or more owing to the shorter separation. In contrast to known line sources, the high yields can even be achieved for narrow substrates and a plurality of simultaneously vaporized materials.
As intermediate carriers, German Patent Application No. 10 2009 007 587.9 indicates endless bands, for example steel bands, as well as circular disk-shaped intermediate carriers.
However, it has been found that endless bands made of steel cannot be produced in a form suitable for use as intermediate carriers. This is primarily because chemically inert steel bands, which are not meant to enter into a reaction with any of the organic materials deposited, are too brittle and therefore appear unsuitable for production as a steel band. Furthermore, it has been found that circular disk-shaped intermediate carriers for use in continuous coating systems with a diameter of more than 1 m cannot be produced with the required accuracy, or if so only with high outlay.
It is therefore an object of the present invention to provide a method and a device which make it possible to coat substrates with materials to be vaporized, in particular organic materials, with high yields.
It is a further object of the present invention to provide a method and a device which permit simultaneous coating of a substrate with materials to be vaporized, while ensuring a reproducible stoichiometry, which is constant inside the deposited layer, of the individual constituents throughout the coating process.
These objects are achieved by a method and a device according to the independent claims. Advantageous configurations of the invention are specified in the other claims.